1. Field of the Invention
The present invention relates to a plasma processing apparatus.
2. Description of the Related Art
A shower head for introducing a gas in a shower shape to a substrate such as a semiconductor wafer has been used to manufacture a semiconductor device or the like. That is, in a plasma processing apparatus for performing plasma etching on a substrate such as a semiconductor wafer, a holding stage on which the substrate is placed is provided in a process chamber and a shower head is provided to face the holding stage. A plurality of gas ejecting holes are provided in a surface of the shower head facing the holding stage and a gas is introduced in a shower shape to the substrate through the gas ejecting holes.
To achieve uniform gas flow in the process chamber, the plasma processing apparatus is configured to exhaust a gas downward around the holding stage. Also, the plasma processing apparatus is configured to change an interval between the shower head, which functions as an upper electrode, and the holding stage, which functions as a lower electrode (as disclosed in, for example, Patent Reference 1).
When the plasma processing apparatus is configured to change the interval between the shower head, which functions as an upper electrode, and the holding stage, which functions as a lower electrode, by vertically moving the shower head, a space (referred to as a rear side space) whose size changes as a size change of a process space needs to be provided at a side opposite to (referred to as a rear side) the process space with the shower head between the rear side surface and the process space. However, the rear side space may adversely affect plasma processing.
That is, abnormal discharge may occur in the rear side space, and the state of plasma in the process space may be changed due to the abnormal discharge or contamination may be caused due to the abnormal discharge. Also, when a process gas is introduced into the rear side space, plasma density or ion concentration in the process space may be reduced or deposits may be attached to a wall surface of the rear side space. Such problems occur not only during etching but also during film formation.
3. Prior Art Reference
(Patent Reference 1) Japanese Patent Laid-Open Publication No. 2000-100789